Candies and power up Lugia???

Lugia is the 4th best psy pokémon. That in itself means, damage wise it's not that great.
14 or 15 attack IV for Lugia would be nice, but your's is a very good pokemon. You could power it up.

Lugia is a good attacker but not consider a first tier due to Its low attack stat. It has some bulk though and can sweep gyms but is not a good attacker in raids.

Here's a post with my opinion from a little while back:

I'll list some points that come to mind for me. Please feel free to disagree or raise some other points of your own.

Pros:
Great "tanky' attacker for Machamp solo raids. If you already have your higher DPS mons and are dying before timing out he could work in more or less the same way that a Dragonite with DT/H does at the end of your lineup.

Good as a general gym sweeper. Depending on what is in there he can probably run through most if not all of it by himself although he will not be especially fast at it.

Sky Attack is a good flying move with STAB. Not a whole lot of good flying move mons with STAB out there right now. That may create some other niche use in the future.

Cons:
When Mewtwo comes out he will fall even further down the rung of psychics for raid purposes where he is not exactly sitting firmly now. And that doesn't include other Psychic mons which will also play a part in future gens.

Stat wise he would be a great defender but he cannot defend.

If you have already powered up DT/H Dragons or have a set working Machamp solo crew it's hard to justify expending resources on Lugia who is at best a lateral move compared to many mons available now. If time is an issue for your solo set he will not help that issue.

While he is a very good gym attacker I feel that the majority of us can already take down most any gym rather easily after the change.

To power him you will likely have to use rare candy. Using rare candy is best imagined as using the best candy for the best mon in the game currently or even mons to come. For example that candy could have been Mewtwo candy. Or tyranitar candy. Or anything. Thus, it is an extremly valuable resource but with a 20K per candy buddy cost it's pretty hard to imagine any justifyable reason to buddy him.

We aren't sure if or when raid bosses will update, rotate or change. When they do, if Machamp is no longer raidable then his arguable use for Machamp soloing is no longer a factor.

90+ IV? I say go for it. However, the major problem with the Legendaries is they require a LOT more investment over other, much better, options.

I have an Articuno that I'm grooming into a Dragonslayer. I have a 91 IV Moltres, but don't know if it want to use it over a 96 IV Charizard. Of course, fires have limited use.

Zapdos appears to be the best of the current bunch, thus far. SHOUT OUT TO TEAM INSTINCT!